Change method for getting external storage on marshmallow

Change method for getting external storage on marshmallow

The new components/features introduced with marshmallow
(vold 3.0) required a new method for retrieving
external/removable storage devices

These changes were based and use part of the following code:
- Storage access implemented on Settings (uses VolumeInfo class
  to list all connected disks (external and emulated)
  see refresh method from class StorageSettings
  => packages/apps/Settings/src/com/android/settings/deviceinfo
  =>  StorageSettings.java

- getVolumeList method from MountService class
  (converts VolumeInfo ArrayList item into a StorageVolume
   element, which is used by CMFileManager to iterate
   contents and build bookmarks):
  => frameworks/base/services/core/java/com/android/server/
  => MountService.java